Sieve frames



. NOV. 26, 1968 HA ET AL 3,412,860

S IEVE FRAMES Filed March 29, 1966 I United States Patent f 3,412,860 SIEVE FRAMES John Dudley Bingham, Bramhail, and Ernest William Higgs, Chinley, via Stockport, England, assrgnorsfo Henry Simon Limited, Stockport, England, a British com an P Eiled Mar. 29, 1966, Ser. No. 538,329 Claims priority, application Great Britain, Mar. 31, 1965, 13,585/65 3 Claims. (Cl. 209379) ABSTRACT OF THE DISCLOSURE A square or rectangular screen is mounted on the upper edges of a nonmetallic frame. The nonmetallic frame comprises self-aligning morticed joints. A rigid, cross-braced metallic frame, L-shaped in cross-section, fits into and supports the non-metallic frame from below so that the bending and twisting loads caused by the tensionmg of the screen are transmitted by the nonmetallic frame members to the metal frame members.

This invention relates to sieve frames.

In sieving machines of a kind such as plans1fters wherein square or rectangular sieve screens, of varlous mesh sizes and made from textile or woven wire fabr cs, are mounted in substantially identical sieve supporting frameworks, it is convenient to fix such screens permanentl y to service frames of a common size which are interchangeable for all sieve supporting frameworks of such a sieving machine. Since it is essential that such screens shall not sag under the weight of the material which may at any time be carried thereon, it is a requirement of such service frames that they shall be sufliciently rigid to withstand without distortion those bending and twisting loads which are transmitted to the frame members as a result of the tension forces inherent in or applied to the screen fabric. It is also a requirement of such service frames that the inner surfaces of the frame walls and the side surfaces of any cross-bracing members shall be of a nature which will resist erosion wear due to multiple impacts by known kinds of free-roving sieve-cleaning members, arranged to pass in a random manner across the underside of the screen to prevent the blinding thereof.

An object of this invention is to provide improved interchangeable sieve screen service frames which satisfy these requirements.

According to this invention, an interchangeable sieve screen service frame comprises, a square or rectangular sieve screen, a four-sided open nonmetallic frame of slender proportions to the upper edges of the walls of which the edges of the screen are fixed, and a rigid crossbraced metal frame arranged to fit into and support the slender open nonmetallic frame from within and from below in such manner that the bending and twisting loads applied to the nonmetallic frame as a result of the tension forces affecting the screen are transmitted by the walls of the nonmetallic frame to the metal frame elements which support them.

In an embodiment of the invention the rigid cross-braced metal frame is a four-sided unit having its opposite side members parallel and at right angles to adjacent side members, the said side members being substantially of L- shaped cross-section with the vertical flanges of all sides towards the inside of the frame and with the horizontal flanges of all sides on a common plane, and there being two cross brace members of substantially the same effective height and effective thickness as the vertical flanges of the L-shaped members, which cross-brace members are 3,412,869 Patented Nov. 26, 1968 arranged with their top and bottom edges flush with those of the said vertical flanges and with their end extremities abutting against and rigidly fixed to, opposite frame side members at positions midway along their lengths, the two cross-brace members being joined together at right angles at the geometric centre of the frame.

The open nonmetallic frame is four-sided with opposite sides parallel and at right angles to adjacent sides, the cross-section of the side members being rectangular and of such height and breadth that when nested into the corner of the cross-section of the metal frame sides, the upper face and the outer side face of the nonmetallic frame member are both flush with the edges of the adjacent metal flanges. Each said frame side member has a horizontal mortice slot at one of its end extremities and a matching horizontal tenon at its other end extremity so that when the four sides are assembled together the morticed joints at the corners of the frame serve to lock all members together on a common plane.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a plan view of a sieve frame according to the invention,

FIGURE 2 is a side elevation in cross-section about the line AA of the sieve frame shown in FIGURE 1,

FIGURE 3 is an enlarged cross-sectional view of any one side of the sieve frame, and

FIGURE 4 is an enlarged isometric view of a corner of the sieve frame.

The interchangeable sieve screen service frame shown comprises a square sieve screen 1 which is fixed along its edges to the top surface of a slender open nonmetallic frame 2 that is supported along the full lengths of all four of its sides by an open rigid cross-braced metal frame 3 the four sides of which are at right-angles to adjacent sides and are substantially L-shaped in cross-section, the said sides being arranged with their vertical flanges 4 towards the inside of the frame and their horizontal flanges 5 on a common plane. At the outer extremity of the horizontal flange of each side of the metal frame 3 there is a downwardly turned lip 6 which provides that in the underside of the frame formed by the said sides there is a shallow recess 7 in which a bottom closure wire-grid 8 can be housed. Joining opposite sides of the metal frame and rigidly fixed to the vertical flanges 4 thereof at positions midway along the flange lengths and with their top and bottom extremities flush with those of the said vertical flanges are two cross-brace members 9 which are rigidly joined together at rightangles at the geometric centre of the frame, each crossbrace member being of the same effective height and effective thickness as the said vertical flanges 4 and comprising a metal lower part -10 and an upper resilient part 11 which fits into a longitudinal slot 12 of the lower metal part 10 in such manner as to constitute a cushion between the underside of the sieve screen 1 and the top edge of the said metal part.

The nonmetallic frame 2 is made of wood and comprises four side members 13, each of which in cross-section is rectangular and of such height and breadth that, when nested into the corner between the vertical and horizontal flanges 4 and 5 of the associated side of the metal frame 3, the upper face and the outer side face of the wooden frame member are both flush with the edges of the adjacent metal flanges. At one end of each member 13 there is a horizontal tenon 14 and at the other end there is a matching horizontal mortice slot 15, the position, length and thickness of the tenon, and the position, depth and width of the mortice slot being such that with the members 13 assembled together so as to provide right-angled corners between adjacent members,

the said members are locked on a common plane and lie snugly against the surfaces of the metal frame flanges.

Fixing screws 16 are provided to lock together the wooden frame 2, the horizontal flanges 5 of the sides of the metal frame 3, and a bottom closure wire-grid 8 arranged to seat in the recess of the metal frame and encage at least one free-roving sieve-cleaning member 17 of known kind in each of the four sieve sections formed by the cross-bracing members 9.

To assemble such a sieve screen service frame, the rigid cross-braced metal frame is arranged with its horizontal flanges downwards, and the nonmetallic frame side members are nested into the metal frame side members with the morticed joints at the corners of the nonmetallic frame engaged; then a screen to which the appropriate stretching tension is applied is brought into engagement with the upper surfaces of the composite frame walls, and is fixed to the upper surface of the nonmetallic frame by staples, or by staples and a suitable adhesive medium, or by other equivalent means. Thereafter the tension forces affecting the screen will hold the side members of the nonmetallic frame in intimate engagement with the vertical flanges of the side members of the rigid cross-braced metal frame. The composite frame is then turned over, sieve-cleaning members are placed in each of the four sieve sections, the Wire-grid 8 is located in its retaining recess 7 and fixing screws 16 are threaded through mesh openings in the wire-grid and through prepared holes in the flanges of the metal frame and are driven into the side members of the non-metallic frame to lock all frame parts solidly together.

It is a particular advantage of a sieve screen service frame in accordance with the invention that, due to its composite nature, it makes available a considerably larger sieving area than can be obtained with an all-wooden sieve screen service frame of equal rigidity, and is considerably cheaper than an all-metal sieve screen service frame of equal rigidity which requires the provision of conventional forms of the clamping means used to fix sieve screens to metal frames.

What is claimed is:

1. A sieve screen service frame for any of a plurality of substantially identical sieve supporting frameworks of a sieving machine, comprising, a square or rectangular sieve screen, a four sided open nonmetallic frame to the upper edges of which the edges of the screen are fixed, and a rigid cross-braced metal frame whereof the side members are of substantially L-shaped cross-section with the vertical flanges of all sides towards the inside of the frame and the horizontal flanges of all sides on a common plane which metal frame is arranged to fit into and support the open nonmetallie frame from within and from below in such manner that the bending and twisting loads applied to the nonmetallic frame as a result of the tension forces affecting the screen are transmitted by the side members of the nonmetallic frame to the metal frame elements which support them, characterised in that the corner joints of the nonmetallic frame are self-aligning morticed joints which serve to locate all side members of the nonmetallic frame on a common plane and in intimate contact with associated vertical flanges of the metal frame which side members are of rectangular cross-section and of such height and breadth that when nested into the corner of the associated side of the metal frame the upper face and the outer side face of each nonmetallic frame member are both flush with the edges of the adjacent flanges.

2. A sieve screen service frame according to claim 1, wherein the rigid cross-braced metal frame has those surfaces of the vertical flanges of its L-shaped side members that are remote from the non-metallic frame so sloped that the vertical flanges are thicker at the bottom than at the top, and there being two cross-brace members joining opposite sides of the said metal frame and being rigidly fixed to the vertical flanges of the frame side members at positions midway along the flange lengths and with their top and bottom extremities flush with those of the said flanges the said cross-lbrace members being rigidly joined together at right angles at the geometric centre of the frame and each crossbrace member being of the same effective height and effective thickness as the said vertical flanges and comprising a metal lower part and an upper resilient part which fits into a longitudinal slot in the lower metal part in such manner as to constitute a cushion between the underside of the sieve screen and the top edge of the said metal part.

3. A sieve screen service frame according to claim 1 wherein means which positively lock the nonmetallic frame to the metal frame also serve to fix to the metal frame a bottom closure Wire-grid which encages within the confines of the metal frame such free-roving cleaning members as are required to prevent the blinding of the sieve screen when in use.

References Cited UNITED STATES PATENTS 146,065 12/1873 Hale -371 758,907 5/ 1904 Fraser 2093'19 X 2,042,072 5/ 1936 Robins 209403 2,114,406 4/ 1938 Simpson 209408 X 2,181,605 11/1939 Norvell 209-408 2,345,947 4/1944 Parks 209-403 FOREIGN PATENTS 1,080,684 6/1954 France.

HARRY B. THORNTON, Primary Examiner.

ROBERT HALPER, Assistant Examiner. 

